1. Field of the Invention
The present invention relates to a vehicle navigation system. More particularly, the present invention relates to a vehicle navigation system that uses a portable information terminal (hereinafter, to be referred to as “PDA”).
2. Description of Background Art
In recent years, many vehicles use vehicle navigation systems that guide the drivers to their goals on a map on which the current position of the vehicle is displayed respectively. Such navigation systems are realized by combining a global positioning system (GPS) and map information.
Conventionally, vehicle navigation systems have been developed mainly for four-wheel cars. In recent years, however, it is under examination whether or not it is possible to install these systems also in small cars such as auto-bicycles, irregular ground buggies, etc. For example, the official gazette of Published Unexamined Patent Application No. 11-321754 discloses an auto-bicycle in which a navigation system is installed.
Conventional navigation systems have employed large display screens so as to provide the drivers with as much information as possible. For such small vehicles as auto-bicycles, etc., therefore, it has been difficult to secure a space for mounting such a display panel in the visual field of the driver.
In order to solve such the technical problem, the official gazette of Published Unexamined Patent Application No. 11-14391 or No. 10-122885 proposes a method that displays only the minimum necessary information, such as a direction of and a distance to a goal, in a small area of the vehicle meter panel as in a small portable GPS unit.
According to the above-described conventional techniques, operation switches must be disposed in a limited area on or around the meter panel, making the units difficult to operate. This, then, presents another problem with conventional devices.
In addition, because it is difficult to provide the driver with enough information on the above-described rough display, the navigation system must be able to prepare a dedicated map on which longitude and latitude lines are described in detail, and further, must also provide a portable GPS unit to let the driver know his/her current position with accuracy.
Under such circumstances, it is an object of the present invention to provide a vehicle navigation system with excellent operability that can provide the driver with the minimum necessary route guidance information when driving the vehicle, thus solving the conventional technical problems described above.